1. Field of the Invention
This invention relates generally to penile prostheses and more specifically to parylene-coated components used therefor.
2. Description of the Related Art
The implantation of a penile prosthesis is one known treatment for the condition in human males known as erectile dysfunction or ED. Once implanted, the penile prosthesis is used to artificially create an erection, thus allowing the patient to be sexually active.
Such prosthesis generally includes a pair of inflatable cylinders which are implanted, in parallel, in the patient""s corpus cavernosae. The prosthetic also includes a pressurized reservoir of fluid that is implanted elsewhere in the patient""s body, usually in the abdomen. A pump and valve assembly is fluidly coupled to the reservoir via reservoir tubing and the pair of inflatable cylinders are then fluidly coupled, via fluid passageways, to the pump and valve assembly. Upon actuation of the pump and valve assembly, the cylinders become pressurized due to fluid transfer from the reservoir to the pump and valve assembly and from the pump/valve to the cylinders which, in turn, causes the cylinders to become rigid. This rigidity thereby causes the desired erection.
There are several variations of such a prosthetic. For example, the cylindrical members can expand as they are pressurized, or in another variation, they may simply go from an empty, flaccid state to a full, rigid state, with no expansion of the cylinder(s). The reservoir and/or the pump assembly can also be made integral with the cylinder(s).
In order to adapt the prosthetic to the patient""s anatomy, the cylinders have arcuate front and rear cap portions which mate well with the ends of the corpus cavernosae. Moreover, the caps serve to form a sealed chamber within the cylinder thus enabling the cylinder to inflate.
In order to control the expansion of the cylinder as it is inflated, a sleeve of fabric or other cloth-like material is placed around an inner tube of the cylinder. Thus, the diameter of the cylinder can only expand to a size congruent with the fabric sleeve. The use of a fabric sleeve also effectuates a uniform inflation. Typically, a second sealed outer tube is placed around the inner tube and the fabric sleeve. Thus, a typical cylinder wall includes two tubes, one within the other. Consequently, proper functioning is dependent on the correct operation of the inner tube and, in some embodiments, on the correct operation of the outer tuber as well. That is, in some cases, the area around the outer tube is used for fluid transfer and/or storage. A fabric sleeve may also be used with those types of cylinders that do not expand when filled, but simply become rigid.
The double walled structure is an efficient arrangement. One potential issue is the continuous contact between each of the tubes and the fabric. The prosthetic exists in a relaxed or flaccid state a majority of the time and thus the inner and outer tubes are in contact with the fabric a majority of the time. The specifics of this situation are elaborated below.
In order to provide comfort and a better sense of normalcy to the patient, the prosthetic is made from materials that allow the prosthetic to bend and be flexible when in the flaccid state. Such bending, however, may lead to the formation of a crease in the walls of the double-walled or single-walled device. This crease terminates in bend corners that are areas of stress and highly localized areas of contact between the cylinder""s inner and outer tubes and the fabric sleeve. Consequently, as the flaccid cylinder is bent from side to side or generally moved about a central axis due to normal movement of the patient, the bend corners will likewise travel thus resulting in pockets of the cylinder contacting and moving across each other. This results in a movement of the corners which causes portions of the tubes to contact (and move across) each other. There is also a potential element of material fatigue as the various materials are repeatedly stressed and unstressed.
Moreover, since the crease generally occurs in the same location on the cylinder, the same areas of contact are repeatedly moved across each other. Over time, this repeated contact and movement may lead to wear, abrasion, and fatigue.
Typically, the tubes are formed from a versatile material such as silicone or polyurethane which are medically safe and provides the necessary degree of structural reliability. It has been found that silicone has a high coefficient of friction and can be somewhat tacky. As a result, when silicone contacts itself or some other surface, it can bind and resist movement. Indeed, this frictional engagement could cause the contacting surfaces to wear at these contacting locations and eventually could potentially cause the tubing to wear and fatigue.
For the same reasons, similar situations may be encountered with other components of the prosthesis. The fluid passageways, the reservoir, the housing for the pump and valve assembly are all typically made from silicone. Thus, in any instance where the silicone surfaces of these components are caused to bend, to contact other silicone surfaces, or to fatigue, similar situations of wear may be encountered.
The present invention provides a penile prosthesis which has components formed from silicone or similarly flexible material which are coated with a material that increases the strength of the component while also reducing its coefficient of friction. When corners are formed in the flaccid cylinder, for example, increased wear tolerances are exhibited by allowing the components of the cylinder to smoothly move against each other. The coating material allows one surface of the cylinder to slide smoothly against another surface. Thus, wear due to abrasion is significantly diminished. Furthermore, the coating material minimizes fatigue and resists contact stresses.
In a preferred embodiment, both the inner and outer surfaces.of the tube(s) of the cylinder are coated with a very thin layer of parylene. Parylene is an ideal material for this purpose in that it provides a very strong and wear resistant surface, is relatively slippery, is fatigue resistant, and allows for repeated expansion and contraction with no negative effects.
To form the components of the cylinder (or any other tubular component) of the preferred embodiment of the present invention, a silicone tube is sized. Both the inner and outer surfaces of each end portion are then masked. The masking can be done by inserting sections of rigid silicone into the ends of the silicone tube. This rigid insert has an outer diameter approximately equal to the inner diameter of the silicone tube. A wrapping, such as shrink-wrap (heat shrink tubing), is then placed over the outer diameter of the silicone tube, to correspond with the rigid insert. The shrink-wrap is then heated causing it to shrink. This, in turn, causes the silicone tube to compress the rigid insert, thus generating a portion of the silicone tube that is sealed between the rigid insert and the outer wrapping.
The masked tube is then placed in a vapor deposition chamber where vaporized parylene is introduced into the environment. In a known way the vaporized parylene simultaneously coats both the inner and outer surfaces of the silicone tube to a predetermined thickness. The coated silicone tube is then removed from the deposition chamber and the rigid inserts and shrink-wrap are removed from the coated silicone tube. Appropriate end caps are attached and adhered to the non-coated portions, thus forming a complete cylinder. Alternatively, coating just the inner or the outer surface will also lead to increased wear characteristics.
In addition, any of the other components of the penile prosthesis could likewise be coated, thus realizing increased wear characteristics.
For those cylinders utilizing a double wall structure, it is optimal to coat the inner and outer surfaces of both tubes forming the completed cylinder. Increased wear characteristics are achieved, however, even when just the inner or outer surfaces are coated.
The present invention includes applying a coating of a material such as parylene to one or more components of a penile prosthesis. This is applicable to virtually any type or style of prosthesis. Namely, whether a single or double walled cylinder is utilized, whether expandable or non-expandable cylinders are utilized, or whether the components (cylinders, pump assembly, reservoir, etc.) are separate or integral, the coating will be advantageous.
Yet another aspect of the present invention is the application of parylene, or a similar material to a variety of implantable devices, commonly formed from silicone or a like material. As specifically detailed herein as the preferred embodiment, a penile prosthesis having connected but separate components (cylinders, reservoir, pump) will benefit greatly by having a coating of a material such as parylene applied to one or more of those components. In addition, many penile prosthetics come in different configurations. A reservoir may be made integral with the cylinder, or all of the components may be made from one integral unit. As referred to herein, the penile prosthesis is meant to include any and all of these various forms, as they may all benefit from the application of a material such as parylene.
In addition to the penile prosthesis, other implantable devices are commonly formed from silicone or other flexible materials and can benefit from the application of a coating of parylene. For example, testicular implants are sometimes implanted into a male patient to return a sense of normalcy to that patient. Such implants may be implanted during the implantation of the penile prosthesis to minimize surgical exposure. Testicular implants can be formed as elliptical or oval silicone blocks. These blocks are generally solid, but could be fluid filled. In either event, the application of parylene of a like material will reduce the effects of frictional engagements as the implants are moved about. In addition, the coating may serve to contain the material forming the implant, thus preventing leakage into the patients. For this reason, it is also desirable to apply parylene to silicone breast implants. The parylene will serve to contain the fluid filled implant and will reduce the abrasive effects cause by the normal movement of the implant.
Another type of implantable device within the scope of the present invention is an artificial sphincter. An artificial sphincter is somewhat similar in form and function to the penile prosthesis. Namely, a reservoir and a pump are provided and are coupled to an inflatable member. The inflatable member is positioned so that when inflated, it exerts pressure on the urethra or bladder neck, in the case of artificial urinary sphincters, or the rectum in the case of artificial bowel sphincters. As pressure is applied, the rectum or the urethra is effectively sealed, thus preventing incontinence. These devices can come in various forms; i.e., those with separate components connected by tubing or those having certain parts combined into an integral unit (pump combined with reservoir). Whatever their form, it is advantageous to coat the various components with parylene or a like material. The coating serves to minimize the effects of frictional engagement and will increase the life expectancy of the product.